Aiming at the evaluation of the occurrence of thyroxine and progesterone-17-alpha-OH circadian rhythm, 4 adult crossbred swine females (non-pregnant and showing no estrous signs) were studied, reared and kept under a industrial management system. Hormone determinations were assessed by solid phase radioimmunoassay (RIA)ª. Thyroxine serum analysis showed the highest concentrations around 3:00 PM and decreased until reaching the lowest values at the 0:00 to 4:00 AM interval. Regarding progesterone-17-alpha-OH, the highest concentrations were observed at 3:00 AM, showing a progressive decrease along the day until reaching lower values at the 12:00 to 3:00 PM interval.
Circadian rhythm; Hormone; Swine
